The scope of the present invention is motorcycle frame layout and suspension structure.
Motorcycles are designed today to be as compact and lightweight as practical in the face of many competing requirements. In the area of frame and suspension requirements, the location of cushion members such as spring and damping units has been the subject of a continuing effort at compromise and study. Closely related thereto is the design of frame members for supporting the various components of the motorcycle and rigidly accommodating the forces subjected thereon by the suspension system and cushion members. Efforts have been made to locate such cushioning members inwardly on the motorcycle in the area between the engine and the rear wheel. However, such devices have interfered with such essential factors as fuel tank location, tank capacity, air cleaner and electrical accessory space and the like and have inevitably resulted in compromise in design. Furthermore, such inboard cushioning systems have generally required extension of the wheel base to accommodate all components including cushion members. Extension of the wheel base results in unwanted additional overall weight and the necessity for additional structural rigidity. Frame systems requiring additional structural rigidity often require interference with the access to and removal of components of the motorcycle, particularly the engine. Thus, additional compromise is often required.
Additionally, difficulties have been experienced in the fabrication of suspension systems capable of withstanding the loads imposed and the number of cycles experienced over the life of a motorcycle. Increased loading can be experienced in inboard cushioning systems because of the short moment arm distances through which the cushion member acts. As a result, careful alignment of the components and close tolerances have been required, particularly in the area of the pivot mechanism for a pivoted trailing rear fork system employing inboard cushioning mechanisms.